Very nice! Thanks for the heads up, Greg. I looked through it, and these look like hosted payment services comparable to PayPal's Website Payments Standard. As such, I think they'd operate as payment methods, but like PayPal's Express Checkout I'm not sure you'd make them available on the checkout form itself. More like an image button on the cart page.
Their introductory offer is quite attractive, and since Amazon has like 60 million users already, this could be huge. Especially noteworthy is the fact that it can be used for building marketplace e-commerce sites where you take a cut of all transactions processed through your site. People have been wanting to do this in UC for some time, but it just hasn't been possible till now.